This is a prospective, multicenter, observational study of HIV-infected subjects who are CMV-seropositive and who have not had clinical symptoms of CMV disease at study entry. Subjects will be followed for three years or until the diagnosis of CMV end-organ disease, or death, whichever comes first. CLinical evaluations will be performed at baseline and every 16 weeks. Blood samples will also be stored every 16 weeks for future immunologic studies.